Apparatus and methods for inspecting extreme ultra violet reticles

ABSTRACT

Disclosed are methods and apparatus for inspecting an extreme ultraviolet (EUV) reticle is disclosed. An optical inspection tool is used to obtain a phase defect map for the EUV reticle before a pattern is formed on the EUV reticle, and the phase defect map identifies a position of each phase defect on the EUV reticle. After the pattern is formed on the EUV reticle, a charged particle tool is used to obtain an image of each reticle portion that is proximate to each position of each phase defect as identified in the phase defect map. The phase defect map and one or images of each reticle portion that is proximate to each position of each phase defect are displayed or stored so as to facilitate analysis of whether to repair or discard the EUV reticle.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of U.S. Provisional Patent ApplicationNo. 61/659,804, entitled METHOD FOR INSPECTING AND IMPROVING THE QUALITYOF EUV PATTERNED MASKS, filed 14 Jun. 2012 by Mehran Nasser-Ghodsi etal., which application is incorporated herein by reference in itsentirety for all purposes.

TECHNICAL FIELD OF THE INVENTION

The invention generally relates to the field of reticle inspection andmetrology. More particularly the present invention relates to inspectionand measurement of extreme ultra-violet (EUV) reticles (or masks).

BACKGROUND

Generally, the industry of semiconductor manufacturing involves highlycomplex techniques for fabricating integrating circuits usingsemiconductor materials which are layered and patterned onto asubstrate, such as silicon. An integrated circuit is typicallyfabricated from a plurality of reticles. Initially, circuit designersprovide circuit pattern data, which describes a particular integratedcircuit (IC) design, to a reticle production system, which transformsthe pattern data into a plurality of reticles. One emerging type ofreticle is an extreme ultraviolet (EUV) reticle that is comprised of aplurality of mostly reflecting layers and a patterned absorber layer.

Due to the large scale of circuit integration and the decreasing size ofsemiconductor devices, the reticles and fabricated devices have becomeincreasingly sensitive to defects. These defects, if uncorrected, cancause the final device to fail to meet the desired performance due toelectrical timing errors. Even worse, such defects can cause the finaldevice to malfunction and adversely affect yield.

It would be beneficial to provide a system and techniques that aresuitable for inspecting and measuring EUV reticles for defects and usingsuch defect results, for example, for defect evaluation and/or maskrepair.

SUMMARY

The following presents a simplified summary of the disclosure in orderto provide a basic understanding of certain embodiments of theinvention. This summary is not an extensive overview of the disclosureand it does not identify key/critical elements of the invention ordelineate the scope of the invention. Its sole purpose is to presentsome concepts disclosed herein in a simplified form as a prelude to themore detailed description that is presented later.

In general, certain techniques of the present invention combine theadvantages of optical and electron beam (e-beam) inspection tools fordetecting and identifying defects on EUV masks. An optical inspectionincludes detection of phase defects on a EUV mask blank and obtaining aphase defect map with respect to positions on the EUV mask. The blankmask is subsequently patterned by a mask writer. After patterning, ahigh-throughput e-beam apparatus is then used to inspect the patternedreticle with sufficient resolution to detect and characterize patterndefects. The phase defect map may also be used to obtain images at thephase defect positions. The phase defect map, pattern defect map, andreticle pattern may be analyzed together or individually to determinewhether to repair, discard, or use the reticle.

In one embodiment, a method of inspecting an extreme ultraviolet (EUV)reticle is disclosed. An optical inspection tool is used to obtain aphase defect map for the EUV reticle before a pattern is formed on theEUV reticle, and the phase defect map identifies a position of eachphase defect on the EUV reticle. After the pattern is formed on the EUVreticle, a charged particle tool is used to obtain an image of eachreticle portion that is proximate to each position of each phase defectas identified in the phase defect map. The phase defect map and one orimages of each reticle portion that is proximate to each position ofeach phase defect are displayed or stored so as to facilitate analysisof whether to repair or discard the EUV reticle.

In a specific implementation, the method includes using a chargedparticle tool to obtain a pattern defect map for the EUV reticle afterthe pattern is formed on the EUV reticle. The pattern defect mapidentifies a position of each pattern defect on the EUV reticle. In thisimplementation, the pattern defect map is displayed and/or stored inassociation with the phase defect map and one or images of each reticleportion that is proximate to each position of each phase defect so as tofurther facilitate analysis of whether to repair or discard the EUVreticle. In a further aspect, the method also includes (i) prior tousing the EUV reticle in a photolithography process, simulating anexposure pattern that would result from each pattern defect and phasedefect on the EUV reticle based on the phase defect map and the patterndefect map, (ii) prior to using the EUV reticle in a photolithographyprocess, analyzing the simulated exposure pattern to determine whetherone or more pattern or phase defects are predicted to cause a problem ina device that is fabricated with the EUV reticle and whether suchproblem can be mitigated by altering the pattern of the EUV reticle,wherein simulating and analyzing the simulated exposure pattern areperformed without use of a design database that was utilized tofabricate the EUV reticle, and (iii) if one or more pattern or phasedefects are predicted to cause a problem that can be mitigated, alteringthe pattern of the EUV reticle so as to mitigate the problem.

In another aspect, the position of each phase defect is referenced withrespect to a first stage coordinate system of the optical inspectiontool and the position of each pattern defect is referenced with respectto a second stage coordinate system of the charged particle inspectiontool. In this aspect, both the first and second stage coordinate systemsare based on a plurality of fiducial marks of the EUV reticle. In yetanother aspect, the pattern defect map is obtained by compensating fordesign differences between reticle portions that are designed to resultin identical exposed patterns when using the EUV reticle in aphotolithography process and are designed to compensate for at least aflare effect of the photolithography process. In a specific example, thepattern defect map is obtained via multiple beams of the chargedparticle tool scanning simultaneously across the EUV reticle. In oneexample, the multiple beams have a number greater than 25. In anotherembodiment, the pattern defect map is obtained by comparing each of aplurality of test images of the EUV reticle with a correspondingreference image that is determined by performing rigorouselectromagnetic simulations on design data for the EUV reticle so as tomodel fabrication of a reticle model and to model obtaining an image ofsuch reticle model using a charged particle inspection tool.

In yet another example, the method includes analyzing a position of eachof a plurality of phase defects as identified by the phase defect maprelative to a design pattern, which can be used to form the pattern onthe EUV reticle, to determine whether such phase defect is predicted tocause a problem in a device that is fabricated with the EUV reticleafter it is patterned with the design pattern and whether such problemcan be mitigated by altering the design pattern of the EUV reticle priorto forming the pattern on the EUV reticle. If one or more phase defectsare predicted to cause a problem that can be mitigated, the designpattern is altered and the altered design pattern is used to form thepattern on the EUV reticle so as to mitigate the problem.

In other embodiments, the invention pertains to system having an opticalinspection tool configured to inspect a EUV reticle, which isunpatterned, and generate a phase defect map that specifies a pluralityof phase defects and their associated positions on the EUV reticle and acharged particle inspection tool configured to inspect the EUV reticleafter a reticle pattern is formed on such EUV reticle and obtain apattern defect map that specifies a plurality of pattern defects andtheir associated positions on the EUV reticle. The charged particleinspection tool is further configured to obtain an image at each phasedefect's associated position on the EUV reticle The system furthercomprises an analyzer that is configured to perform one or more of theabove methods. In one embodiment, the analyzer is configured fordetermining whether one or more pattern or phase defects are predictedto cause a problem in a device that is fabricated with the EUV reticleand whether such problem can be mitigated by altering the pattern of theEUV reticle.

In a specific implementation, the analyzer forms part of the chargedparticle inspection tool. In another embodiment, the charged particleinspection tool and the optical inspection tool are in the form of anintegrated cluster system. In a specific embodiment, the chargedparticle inspection tool is configured to form a plurality of beamcolumns, and the system further includes a reticle repair tool forrepairing the EUV reticle if one or more pattern or phase defects arepredicted to cause a problem that can be mitigated. In a further aspect,the beam columns are formed by using a magnetic flux by-pass plate withmultiple bores that perturb a large-scale B field so as to producelensing fields for each of the beam columns, and the charged particletool includes the magnetic flux by-pass plate with multiple bores. Inyet another aspect, the charged particle inspection tool is configuredto form more than 25 beam columns.

In another embodiment, the invention pertains to an apparatus forreviewing inspection results for a EUV reticle. The apparatus includes adisplay for displaying images and a controller that is configured toperform one or more of the above methods.

These and other aspects of the invention are described further belowwith reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of a side view of an example EUVreticle.

FIG. 2 illustrates a side view perspective of an EUV reticle and waferin an EUV photolithography process.

FIG. 3 is a flow chart illustrating a combined optical and e-beaminspection of an EUV reticle in accordance with one embodiment of thepresent invention.

FIG. 4A is a side view schematic representation a EUV mask blank inaccordance with certain embodiments.

FIG. 4B is a side view schematic illustration of a EUV mask blanksurface exemplifying an inspection of two types of phase defects inaccordance with certain embodiments.

FIG. 5 illustrates four simulated images of the optical system pointspread function at a focal point and a certain defocused point and shownas an in-phase central spot and out-of-phase (90°) ring.

FIG. 6 is an illustrative plot of contrast as a function of focal pointposition for two types of phase defects.

FIG. 7 illustrates a flow chart corresponding to an optical inspectionprocess for detecting phase defects and/or particles on a surface of anunpatterned object, such as a blank EUV reticle, in accordance withcertain embodiments.

FIG. 8 is a diagrammatic representation of an image of a blank EUVreticle having phase defects.

FIG. 9 is a flow chart illustrating a procedure for inspecting apatterned EUV reticle using a high-speed e-beam tool in accordance witha specific implementation of the present invention.

FIG. 10 is a flow chart illustrating an inspection results analysisprocedure in accordance with a specific embodiment of the presentinvention.

FIG. 11 is a simplified example of a phase defect image and a patterndefect image overlaid on a reticle pattern image in accordance with oneexample.

FIG. 12 is a diagrammatic representation of an example inspection andlithography system in which techniques of the present invention may beimplemented.

FIG. 13 is a diagrammatic representation of some elements of an opticalinspection tool in which techniques of the present invention may beimplemented.

FIG. 14 is a cross-sectional diagram of a multiple-column electron beamapparatus in which certain techniques of the present invention may beimplemented.

FIG. 15 is an exemplary microcolumn of the electron beam apparatus ofFIG. 14.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Thepresent invention may be practiced without some or all of these specificdetails. In other instances, well known component or process operationshave not been described in detail to not unnecessarily obscure thepresent invention. While the invention will be described in conjunctionwith the specific embodiments, it will be understood that it is notintended to limit the invention to the embodiments.

Introduction

An extreme ultraviolet (EUV) lithography process typically uses an EUVtype reticle that is designed to facilitate patterning on a wafer at EUVwavelengths, such as 13.5 nm. FIG. 1 is a diagrammatic representation ofa side view of a portion of an example EUV reticle. As shown, the EUVreticle 100 may include a substrate 102, such a low thermal expansion(LTE) or ultra-low expansion (ULE) glass plate.

The substrate is covered with multiple layers 104 of materials toprovide moderate reflectance (e.g., 60-70% or more) at the EUVwavelength for performing lithographic exposure at EUV wavelengths. Themultilayer stack 104 serves as a Bragg reflector that maximizes thereflection of EUV radiation while being a poor absorber of the EUVradiation. Reflection generally occurs at interfaces between materialsof different indices of refraction with higher differences causing morereflectivity. Although indices of refraction for materials exposed towavelengths that are extremely low are about equal to 1, significantreflection can be achieved through use of multiple layers havingalternating layers of different refractive indices. The multilayer stackalso may be comprised of low absorption characteristics so that theimpinging radiation is reflected with little loss. In certainembodiments, the multiple layers 104 include between about 30 to 40 (or40 to 50) alternating pairs of molybdenum (Mo) and silicon (Si) layersarranged with about 7 nanometer pitch. Other suitable layers may includealternating layers of Mo₂C and Si, Mo and beryllium (Be), molybdenumruthenium (MoRu) and Be.

The multiple layers 104 may be covered with a capping layer 106, such asRu, to prevent oxidation. In other embodiments, an EUV reticle mayinclude a quartz, antireflective coating (ARC), and other features. Apattern (e.g., 108 a and 108 b) is formed in an absorber layer that isdisposed over the multiple layers 104. For example, a tantalum boronnitride film topped by a thin anti-reflective oxide acts as a EUVabsorber. The material(s) used for the reticle pattern may be selectedto have nearly zero etch bias so as to achieve ultra-fine resolutionfeatures.

In general, any suitable EUV photolithography process may be implementedto expose a photoresist layer on a wafer via a EUV reticle. FIG. 2illustrates a side view perspective of a reticle and a wafer sample in aEUV photolithography process. The light source of a photolithographysystem may produce any suitable radiation that is suitable for use withEUV reticles. For instance, EUV wavelengths between about 11 to 14 nm orlower soft x-ray wavelengths may be utilized. In a specificimplementation, a wavelength of about 13.5 nm is produced.

During photolithography, radiation 206 that is reflected from themultiple layers 104 of a EUV reticle is absorbed in a resist layer 202formed on a wafer substrate 204. The absorbed radiation producesphotoacids (H+) and amplified photoacids (e.g., 208 a and 208 b) thatform an exposed pattern in the resist layer 202 of the wafer substrate204 that corresponds to the absorber pattern layer, e.g., 106 a, of theEUV reticle when the photo resist is developed. Reflective imagingoptics between the EUV reticle and the wafer is omitted in FIG. 2 forclarity.

Optical inspection with deep ultra-violet (DUV) or 193 nm lightcurrently is at its limit of being able to detect very small defects inan EUV mask that may cause problems in printing semiconductor waferswith critical features below 22 nm in size. An electron beam (e-beam)inspection tool typically has sufficient resolution to detect such smalldefects. However, an e-beam inspection is not sensitive to phase defectson a EUV mask. Additionally, current single-column e-beam systems tendto be too slow so that they are not practical for inspecting a fullreticle.

EUV Reticle Inspection Embodiments

Certain embodiments of the present invention combine an opticalinspection for finding phase defects on a blank EUV reticle and ahigh-speed e-beam inspection for finding small pattern defects, as wellas imaging reticle locations of the detected phase defects, on apatterned EUV reticle. This combination results in a phase defect mapand a patterned defect map for a particular EUV reticle that may be usedfor defect compensation and reticle repair. These techniques alsoinclude excellent coordinate accuracy of the phase defect map (from theoptical system) and the pattern defect map (from the e-beam system).

FIG. 3 is a flow chart illustrating a combined optical and e-beaminspection 300 of a EUV reticle in accordance with one embodiment of thepresent invention. Using an optical inspection tool, a blank EUV reticleis initially inspected to obtain a phase defect map with respect to EUVreticle positions in operation 301.

In a specific example, a multilayer EUV mask blank is inspected forphase defects, such as bumps and pits, using a specifically configureddeep ultraviolet (DUV) inspection system. The inspection system may uselight in wavelengths less than 193 nm (DUV) or alternatively light ofwavelengths in the 40 to 200 nm range (VUV). In yet another embodiment,the inspection tool may use a 13.5 nm wavelength or the same wavelengthas the photolithography tool in which the EUV reticle is to be used. Anyof these inspection systems may also be configured to perform darkfieldor brightfield inspections.

In a specific example, an inspection system is configured with a partialcoherence sigma of between about 0.15 and 0.5. A reflected light may becaptured by a time delay integration (TDI) detector and passed to acomputer system for analysis. A signal to noise ratio (SNR) can beimproved by applying specially designed filters, thresholds, andcorrection factors. Such specifically configured DUV systems can be usedto detect phase defects as small 1 nanometer in height and 50 nanometersin full width half maximum (FWHM).

FIG. 4A is a side view schematic representation of a EUV mask blank 400in accordance with certain embodiments. As shown, EUV mask blank 400includes a substrate 402, such a low thermal expansion (LTE) glasssheet. The substrate is covered with multiple layers (ML) 404 ofmaterials to provide good reflectance at the EUV wavelength forfacilitating lithographic exposure on a specimen, such as asemiconductor wafer. The multiple layers 404 may include a capping layer406. In other embodiments, a blank reticle includes any number and typeof deposited layers, such as a subset of the ML layers 404 illustratedin FIG. 4A.

A blank EUV reticle may be inspected after each single layer isdeposited on the substrate 402. In another example, the blank EUVreticle is inspected after all or a portion of the ML layers 404 aredeposited, but prior to depositing of the capping layer 406.

EUV mask blanks and other sample types sometimes have surface defects.The defects can be generally characterized as phase defects, such as pit412 and bump 414, and particles 416. These bumps and pits usually arisefrom defects at the substrate, 402. Thus, the layers are typically alsodistorted (although not shown). While bumps and pits are almost purelyoptical phase objects, particles have both amplitude and phasecharacteristics. Both types of defects can be very damaging to EUVlithography and need to be carefully detected and analyzed. For example,a phase shift caused by a 1 nanometer high bump is sufficient to producea printable defect.

Actinic (e.g., 13.5 nanometers) inspection tools can be used forinspection of these defects, but these tools are not expected to beavailable for several years in high throughput configurations suitablefor non-academic uses. Currently available systems have eitherthroughput or sensitivity limitations. For example, multi-beam confocalmicroscopes supplied by LaserTec in Yokohama, Japan detect surfacedisturbances by monitoring reflective signals. However, thesemicroscopes have a poor sensitivity and are generally not suitable forinspection of EUV mask blank defects. Higher illumination powers couldimprove the sensitivity but they are often damaging to EUV mask blanksDark-field 13.5 nanometer microscopes have been proposed for EUV maskblank inspection, but these dark-field systems may be extremely slow andnot suitable for production uses.

Several embodiments for inspecting a blank EUV reticle are furtherdescribed in U.S. Patent Application 2011/0181868, filed 13 Apr. 2011 byStanley E. Stokowski, which application is incorporated herein byreference in its entirety. In general, it has been found that a DUVinspection system can be configured for inspection of small surfacedefects on EUV mask blanks and other similar samples. In accordance witha specific embodiment, the Teron 600 inspection system, available fromKLA Tencor in Milpitas, Calif., has been reconfigured for inspectionphase defects as small as 1 nanometer in height and 80 nanometers FWHMon typical EUV mask blanks. It has been also found that DUV systems canbe also configured for inspecting particle defects.

FIG. 4B is a side view schematic illustration of a EUV mask blanksurface exemplifying an inspection of two types of phase defects inaccordance with certain embodiments. A substantially flat portion 452 ofthe inspected surface is shown as a reference to illustrate phase shiftdifferences in the light beams reflected from the pit 454 and the bump456. It should be noted that a surface roughness produces someadditional phase fluctuations, which become a part of the overallbackground noise. A surface roughness is generally consistent across theentire sample surface, which includes both flat portions (such aselement 452) as well defects (such as elements 454 and 456). As such, aroughness can be at least partially compensated for by applying aspecifically designed filter. Such filter could substantially increase asignal to noise ratio.

When the pit 454 is inspected, the reflected light has the sameamplitude as the reflected light from the flat portion 452. However, thereflected light from the pit 454 has a negative phase difference (Y)when compared to that of the flat surface (X). Likewise, when the bump456 is inspected, the reflected light has the same amplitude, but it nowhas a positive phase difference (Z) in comparison to the reference (X).In certain embodiments, a portion of the inspected surface or the entiresurface can be used as a phase value reference in order to determinephase shifts.

An optical amplitude (D) for laterally small defects can be expressedwith the following formula:

D=exp(iφ) S=1

A phase (φ) corresponds to the mean defect phase integrated over a pointspread function. An optical amplitude (S) of the flat surroundings isset to one. An image contrast can be achieved by mixing multiple opticalamplitudes using a point spread function. Thus, the defect intensitycontrast can be expressed with the following formula:

${{Contrast} \approx {{S}^{2} - {\frac{S + D}{2}}^{2}}} = {{- {\frac{1}{2}\lbrack {1 - {\cos (\varphi)}} \rbrack}} = {{{- \frac{1}{2}}{\sin^{2}( {\varphi/2} )}} \cong {- \frac{\varphi^{2}}{8}}}}$

For small phase values (φ), the sinusoidal function can be approximatedas a linear function.

However, a contrast value is relatively small for shallow defects. Inorder to increase the contrast, an illuminating light beam can bedefocused to shift the relative phases of the flat surroundings (S) anddefect (D). At a focus (depth of focus (DOF) about equal to 0), thepoint spread function has only a real part. However, under defocusconditions (DOF<0 or DOF>0), the point spread function has an imaginarypart that corresponds to a ring shape. This phenomena is illustrated inFIG. 5, which has four simulated images of the optical point spreadfunction at a focal point and a certain defocused point. The images werecaptured as both an in-phase central spot and an out-of-phase (90°)ring. In other words, the image contrast can be achieved by mixing of acentral spot and a ring, which are 90° out of phase with respect to eachother. As such, the contrast or phase defect can be expressed with thefollowing formula:

${{Contrast} \approx {{S}^{2} - {\frac{S + {\; D}}{\sqrt{2}}}^{2}}} = {{\sin (\varphi)} \approx \varphi}$

In this last contrast expression, the contrast value is linearlyproportional to the phase value (φ) for small phase values. Bumps andpits will have opposite contrast signs, and the contrast sign will flipwhen switching from positive to negative DOF. FIG. 6 illustrates a plotof a contrast as a function of a focal point position, i.e., DOF, fortwo types of phase defects. One defect is a bump extending above thesurface and another defect is a pit protruding below the surface. Bothtypes of defects are shown to have the same dimensions, e.g., 1nanometer in height and about 70 nanometers in FWHM, and inspected usingthe same systems, e.g., a DUV inspection system. A contrast is nearlyzero at focus, i.e., DOF˜0. Therefore, phase defects can be inspectedusing one or more defocused positions (DOF<0 or DOF>0). When multipleinspection passes are performed and/or multiple beams used in the samepass, multiple defocused settings may be used. For example, acombination of positive and negative DOFs may be used. In the same orother embodiments, a combination of defocused (DOF<0 or DOF>0) andfocused positions (DOF˜0) may be used.

Focused positions may be used, for example, to detect particles asfurther explained below. Unlike phase defects, particles have differentoptical properties. Particles scatter more light outside of the imagingaperture and are considered to be both amplitude and phase objects.Furthermore, particles are generally larger than typical phase defectsor, more specifically, than a typical height of EUV mask blank phasedefects. Therefore, different DOF are often needed for particledetection than for phase defect defection. More specifically, beingmostly “amplitude objects”, particles are best detected near focus(DOF˜0). However, particles can still provide significant modulationeven at defocused conditions.

In general, certain blank EUV reticle inspection techniques may includeilluminating an inspected surface with a light beam that has awavelength of less than about 250 nanometers. The beam is passed througha collection of optical elements that have a partial coherence sigma ofbetween about 0.15 and 0.5. The beam is focused onto the inspectedsurface at one or more of focused and/or defocused conditions. Areflected light beam is collected by a detector and can be used toconstruct a resultant image of the inspected surface. This operation mayinclude applying various filters and thresholds. Certain embodiments ofa blank EUV inspection technique are described in the paper authored byStan Stokowski, Joshua Glasser, Gregg Inderhees, and Phani Sankuratri,entitled “Inspecting EUV mask blanks with a 193 nm system,” published inthe Society of Photographic Instrumentation Engineers (SPIE) proceedingsof the, volume 7636, pp. 76360Z-76360Z-9 (2010), which paper isincorporated herein by reference in its entirety.

FIG. 7 illustrates a flowchart corresponding to a process 700 forinspecting phase defects and/or particles on a surface of an unpatternedobject, such as a blank EUV reticle, in accordance with certainembodiments. This process can be used to detect phase defects that areless than about 10 nanometers in height and less than about 200nanometers in FWHM. In more specific embodiments, these techniques areused to detect phase defects that are less than about 5 nanometers inheight, and 150 nanometers in FWHM, or less than about 3 in height and100 nanometers in FWHM, or less than about 2 nanometers in height and 80nanometers in FWHM, or even less than about 1 nanometer in height and 50nanometers in FWHM. An unpatterned object may be a EUV mask blank or anyother similar unpatterned object. In certain embodiments, a surface ofthe inspected object includes quartz and/or an anti-reflective coating(ARC).

The process 700 may start with generating an illuminating light beam inoperation 702. In certain embodiments, an illuminating light beam has awavelength of less than about 250 nanometers. More specifically, anilluminating light beam may be at DUV or EUV wavelengths. Variousillumination sources, such as lasers, can be used for this purpose.

The process may proceed with passing an illuminating light beam througha collection of optical elements in operation 704. Some examples ofoptical elements include condenser lenses, projection lenses, beamsplitters, mirrors, beam steering devices, and beam conditioners. Thecondenser and projection lenses may be selected such that theirnumerical apertures result in a partial coherence sigma of theinspection system to be between about 0.15 and 0.5. It should be notedthat a partial coherence sigma is a ratio of a condenser lens numericalaperture to a projection lens numerical aperture. In certainembodiments, a partial coherence sigma is between about 0.2 and 0.4 or,more particularly, between about 0.25 and 0.3, or between about 0.15 and0.3, or between about 0.15 and 0.2.

An illuminating light beam may then be focused on a surface of theinspected sample in operation 706. A defocus range may be between about+1 and +3 DOF, between about −1 and −3 DOF, or between about +1 and −1DOF. In specific embodiments, absolute DOF values (representing bothnegative and positive DOF ranges) are between about 1.25 and 2.75 or,more particularly, between about 1.5 and 2.5, or even about 2. Incertain embodiments, focusing operations may be accomplished byilluminating the surface with multiple illuminating beams at differentDOFs and/or repeating inspection passes of the surface with light beamsat different DOFs. For example, two beams may have DOF values that areopposite in sign. More specifically, one beam may have a DOF of betweenabout +1 and +3 DOF, while another at between about −1 and −3 DOF. Inanother example, one beam may be defocused at between about +1 and +3DOF, while another beam may be in focus. The second (in-focus)illuminating beam may generate an image (i.e., a focused image) fordetecting particles and other contaminations. In general, multipleimages generated at different DOF can be used to classify defects intophase and surface contamination defects. In certain embodiments,multiple images may be summed up during construction of a resultantimage in later operations.

The process 700 may continue with inspection of the surface in operation708 and then capturing one or more reflected light beams using one ormore detectors in operation 710. A reflected light beam or at least acaptured portion of that beam can be characterized based on a resolutionof the detector. In certain embodiments, a reflected light beam's scanpath across the detector is between about 100 pixels and 1000 pixelswide along a scanning direction or, more particularly, between about 300pixels and 600 pixels wide. A length of the beam path may be at leastabout 500 pixels or, more particularly, at least about 1000 pixels. Ifmultiple reflected beams are produced, then a multi-field detector canbe used to captures these beams.

The process 700 may proceed with constructing a phase defect image andmap in operation 712. This construction process may involve summingmultiple images, applying various filters, thresholds, and/orconcentration values, as well as performing other techniques.

Since EUV mask blanks are unpatterned objects, most or nearly allsystematic noise sources can be eliminated during these operations. Forexample, a systematic noise can be monitored and filtered from thedetected signal or image. By eliminating most of the systemic noise, theremaining signal can still contain some random noise, shot, and speckle.However, an actual non-noisy signal and signals produced by these noisefactors have different spatial power spectra and can be decoupled fromeach other. Therefore, a filter can be designed and applied to furtherimprove a SNR. It has been found that better “matched” filters can bedesigned when a partial coherence sigma is set to less than about 0.25,or even less than about 0.20.

In certain embodiments, a correction factor is applied to remove asystematic noise from the resultant image caused by pixel-to-pixeldifferences in the TDI gain and offsets. For example, a correctionfactor may be determined from a calibration procedure and applied duringinspection/scanning. Further, as inspection occurs, in the absence ofany detected defect, the mean value of each pixel row is monitored anddetermines the correction factor applied.

In certain embodiments, analyzing the resultant image comprises applyinga threshold signal value of at least about 7 to detect phase defects. Athreshold signal value is defined as a ratio to a standard deviation ofthe noise signal. Another way of increasing SNR is to perform multipleinspection passes. However, each additional inspection pass slowsinspection system throughput.

In certain embodiments, an illuminating light beam is focused onto thesurface at a substantially normal angle, which results in illuminatingand reflected light beams sharing their paths. In other embodiments, anilluminating light beam is focused onto the surface at an oblique angle,and the illuminating and reflected light beams do not share their paths.In another embodiment, a zero order component of the reflected lightbeam may be further attenuated prior to reaching a detector.Furthermore, a phase of the zero order component of the reflected lightbeam can be shifting using an imaging aperture in order to improve thecontrast and a signal-to-noise ratio.

The phase defects may be analyzed prior to patterning the EUV reticle soas to mitigate the effects of one or more of the phase defects. Forinstance, the design database may be used to simulate the reticlepattern. The phase defects' locations with respect to such simulatedreticle pattern may then be analyzed to determine whether the reticlepattern's fabrication can be altered to mitigate the effects of one ormore phase defects. Several techniques for altering a reticle pattern'sfabrication are described further in U.S. Patent Application2012/0238096 by Yalin Xiong and Stanley E. Stokowski, filed 12 Mar.2012, which application is herein incorporated by reference in itsentirety. Fabrication of a reticle can include moving one or moreportions of the reticle pattern with respect to a phase defect, removingmaterial from a line trace so as to create more distance between suchline trace and a phase defect, adding material to a line trace so thatthe line trace substantially covers a phase defect, etc.

Any suitable technique may be used to associate the detected phasedefects with a particular position on the reticle to obtain a phasedefect map for the EUV reticle so that such phase defect map can belater analyzed for reticle repair or deposition. For example, locationsof the resulting phase defect image may be determined in relation to oneor more fiducial marks on the reticle. FIG. 8 is a diagrammaticrepresentation of an image of a blank EUV reticle 800 having phasedefects (e.g., 804 a and 804 b) although illustrated as havingexaggerated sizes. As shown, the phase defects 804 a and 804 b are darkintensity values overlaid with the full reticle area 800, which is abright intensity, although the phase defects and reticle could have anyrelative intensity.

The fiducial marks (e.g., 802 a, 802 b, and 802 c) may define aparticular orientation of the reticle and detected defects, for example,with respect to the stage position in the inspection tool. Additionally,these fiducial marks are preferably designed to be seen by both by anoptical and electron beam inspection tool. For instance, the marks arecomprised of a material and have a particular size, height, and shapethat are selected so that the marks result in clear images wheninspected by both an optical and e-beam tool.

The particular inspection tool (e.g., optical or e-beam) may beconfigured to determine accurate coordinates for each detected defect(or a position of the stage on which the reticle resides) with respectto the reticle's fiducial marks. For instance, the tool can accuratelymeasure to 30 nm or less the position of the stage (and correspondingdefect) on which the reticle resides. The stage coordinate system isreferenced to the reticle's fiducial marks so that any defects that aredetected then have an accurate position relative to the mask fiducialmarks. For example, the phase defects can be located and referenced withrespect to these fiducial marks so that the phase defects have a samereference frame as the locations of the reticle pattern and otherdefects, such as pattern defects. For example, an image can include thephase defects at particular locations on the reticle relative to thefiducial marks. These fiducial marks can be used to align the detectedphase defects, as well as other detected pattern defects, with thereticle pattern that are also located relative to such fiducial marks.For instance, an image that includes the phase defects and the fiducialmarks can be aligned with an image of the reticle pattern that alsoincludes such fiducial marks by aligning the corresponding fiducialmarks from each image. For instance, the edges of each cross-shaped canbe aligned in both an x and y direction. A differential intensity signalcan also be calculated from the intensity signal for each fiducial markand used to more accurately locate the edges of each fiducial mark. Eachdefect's location can then be determined relative to such edges, as wellas relative to the reticle pattern. In another embodiment, thecoordinates of each defect relative to origin coordinates of thereticle, as defined relative to the fiducial marks, may be stored in atable of defect locations. Each defect location may also reference acorresponding defect image and/or defect data, such as size and shape.The position of the reticle pattern can also be referenced with respectto such reticle origin.

Referring back to the inspection process of FIG. 3, the EUV reticle maythen be patterned in operation 302. For instance, any suitablepatterning technique is used to deposit and pattern a material, such asan absorber layer, onto the reticle. Specifically, after an absorberlayer may be deposited on the reticle, a photoresist layer is thenpatterned on the reticle. The photoresist layer is then exposed to forma particular exposed design pattern and etched into a particularphotoresist and underlying absorber pattern based on the exposed designpattern.

Using a high-speed e-beam inspection tool, phase defect images may thenbe obtained at positions that are identified in the phase defect map,which was obtained from the blank EUV reticle, in operation 304.High-definition e-beam images at the phase defect locations mayfacilitate review of the reticle pattern in relation to the detectedphase defects. For example, a reviewer may determine whether phasedefects are in a position relative to the reticle pattern that wouldaffect the wafer printing process (e.g., a phase defect is positionedbetween two traces of the reticle pattern).

Using a high-speed e-beam inspection tool, the patterned EUV reticle maythen be inspected to obtain a pattern defect map with respect to the EUVreticle positions in operation 305. Inspection of a patterned EUVreticle may generally be accomplished by a die-to-die, cell-to-cell, ordie-to-database type of inspection. However, such reticle patterninspection may include techniques for compensating for die-to-diedifferences (or the like) that are purposely designed into the EUVreticle patterns.

Prior to use of EUV lithography, other types of optical reticle patternswere designed to have identical die patterns that produce identical dieson a wafer. In contrast, EUV reticles are designed to have different diepatterns to produce identical dies on a wafer. One of the reasons forthis is that the field of the lithography projector has an arc-shape.The wafer and the reticle are synchronously scanned through the field,in a direction that is perpendicular to the arc. The azimuthal angle ofthe chief ray on the mask varies along the arc-shaped field. Differenttypes of features, such as horizontal vs.

vertical features with respect to the beam scan, also cause a differentshadow effect. This difference varies along the arc. Therefore, diesaligned in the scan direction are more similar than dies on differentfield locations.

A second reason for dies having different patterns on the reticle isthat the edge of a die that is also at the edge of the exposure fieldcan differ from the edge of a die that is internal to the exposurefield. The lithography projector steps the wafer and repeats the scan inan unexposed portion of the wafer. The edges of neighboring exposurefields overlap. The overlapping edge is exposed twice and corners can beexposed four times. No circuit pattern is multiply exposed, and measuresmay be taken to reduce the reflection of the reticle at the edge of theexposure field. Nevertheless, the double exposure can cause a subtledifference in the flare exposure at the edge of the exposure field.

A third possible reason for differences between die patterns on thereticle is that different portions of the light with respect to thelithography tool's field of view (FOV) will exhibit different scatteringproperties. For instance, light from different optical paths (e.g.,different angles and different surface smoothness characteristics) willscatter differently across the FOV. The reticle patterns need to bedesigned to compensate for this different scattering, commonly referredto as flare effect. Accordingly, different FOV positions of the reticlepattern may be designed differently to compensate for different flarelevels and different azimuth angle of the chief ray.

Since the reticle will tend to contain different die patterns fordifferent FOV locations for flare correction, it may be difficult todetect defects across the reticle using die-to-die inspection. That is,the detected defects for a reticle may be skewed by the differences thatwere designed into the reticle pattern to compensate for flare andazimuthal angle dependence of the chief ray.

In one inspection and measurement approach, a die-to-database inspectionis used to avoid issues in the design data due to flare compensation andvertical/horizontal bias. FIG. 9 is a flow chart illustrating aprocedure 900 for inspecting a patterned EUV reticle using a high-speede-beam tool in accordance with a specific implementation of the presentinvention. The inspection procedure 900 may be performed on the reticleafter fabrication of such reticle and prior to such reticle being usedin a photolithography process and again at any time after the reticlehas been used in one or more photolithography processes. Additionally,the following operations may be applied with respect to the entirereticle or repeated for a plurality of sub-portions of such reticle. Thee-beam tool may have a single column for obtaining a single image of thereticle at a time or preferably have multiple columns for simultaneouslyobtaining multiple images from multiple portions of the reticle.

Although not required, the operations of FIG. 9 can be performed inparallel for multiple portions of a reticle. Regardless of how theentire reticle image is obtained, the reticle image can be defined asplurality of patch images that are processed by a plurality ofprocessors. The reticle patches may be distributed to processors thatoperate on the test patch data in parallel.

Initially, a test image of a EUV reticle may be obtained in operation901. In one embodiment, patch portions of the reticle can be scannedusing one or more e-beam columns to obtain image data from the entirereticle. Each patch may contain a single die or multiple dies. A patchmay have any size and shape, depending on the particular system andapplication requirements. In general, an image of each patch portion maybe obtained by scanning the reticle in any suitable manner. By way ofexample, a plurality of patch images may be obtained by raster scanningthe reticle with multiple e-beams. Alternatively, the images may beobtained by scanning the reticle with any suitable pattern, such as acircular or spiral pattern. Of course, the sensors (one or more) mayhave to be arranged differently (e.g., in a circular pattern) and/or thereticle may be moved differently (e.g., rotated) during scanning inorder to scan a circular or spiral shape from the reticle.

In one example, the reticle moves past a set of sensors (e.g., ofmultiple e-beam columns) of an inspection tool, and each electron beamscans rapidly back and forth along a line. Secondary electrons aredetected from each region of beam-sample interaction. The path of eachbeam on the reticle, therefore, forms a rectangle, thus resulting inmultiple parallel rectangular scanned areas (each of which is referredto as a “swath”) on the reticle. The detected secondary electrons areconverted into an image of the swath. In this embodiment, the sensors ofthe inspection tool are arranged in a rectangular pattern to receivesecondary electrons from the reticle and generate therefrom image datathat correspond to multiple parallel swaths of the reticle. In aspecific example, each swath can be about 1 million pixels wide andabout 1000 to 2000 pixels high. In one example, each pixel has a size of5 nm.

Each set of image data may correspond to one or more swaths of thereticle. Each set of image data may be obtained by sequentially scanningswaths from the reticle in a serpentine or raster pattern. For example,a first set of swaths of the reticle 600 are scanned by the multipleelectron beams of an e-beam inspection system from left to right toobtain a first set of image data. A set of second swaths are thenscanned from right to left to obtain a second set of image data. Eachset of swath data may also be divided into patches.

Image data for each patch may be obtained using an e-beam inspectiontool that is set up in any suitable manner. For an EUV reticle, ane-beam inspection tool can be generally set up with a set of operatingparameters or a “recipe” for obtaining image data from a patterned EUVreticle. Recipe settings may include one or more of the followingsettings: a setting for scanning the reticle in a particular pattern,focus setting for one or more incident beams, extractor voltage of oneor more beam sources, one or more electrode voltage settings, pixelsize, blanking plate setting for each e-beam column, setting forgrouping adjacent signals from single signals, illumination or detectionaperture settings, incident beam angle settings, other detectorsettings, etc.

A design database may be provided in operation 902. An integratedcircuit design may be developed using any method or system known in theart such as electronic design automation (EDA), computer aided design(CAD), and other integrated circuit design software. Such methods andsystems may be used to generate a design database from the integratedcircuit design. The design database includes data representing aplurality of layouts for various layers of the integrated circuit. Datain the design database may be used to determine layouts for a pluralityof reticles. A layout of a reticle generally includes a plurality ofpolygons that define features in a pattern on the reticle. Each reticleis used to fabricate one of the various layers of the integratedcircuit. The layers of the integrated circuit may include, for example,a junction pattern in a semiconductor substrate, a gate dielectricpattern, a gate electrode pattern, a contact pattern in an interleveldielectric, and an interconnect pattern on a metallization layer.

The design database may include designations identifying different typesof regions of the reticle, different types of features on the reticle,and/or different portions of features on the reticle. The differenttypes of regions, features, or portions of features may include, forexample, critical and non-critical regions, features, or portions offeatures as described in more detail herein. The designations may varydepending upon a design database generated from an integrated circuitdesign or layout.

Data representing a layout of a reticle and designations may have anyform readable by a processor coupled to an inspection system or aprocess tool. For example, the data may include files or other readabledata including one or more features and spatial positions within thereticle associated with the features. Each feature may also include oneor more polygons or other shapes as described herein and a spatialposition within the reticle may also be associated within each of thepolygons or shapes. Therefore, the data can be used to fabricate areticle.

The design database may be used to simulate a reference reticle imagefrom the design database. The reference image may be determined byperforming rigorous electromagnetic simulations on the design data so asto model the construction of a reticle model from such design data andmodel e-beam inspection of such reticle model to generate a referenceimage. For instance, the model simulates a reticle pattern by simulatinga process for altering the design data patterns in a same way as suchdesign patterns are altered to form the actual test reticle, e.g.,corners of the design polygons are rounded, etc. The model alsosimulates a reference image that is generated from such simulatedreticle pattern by modeling the particular inspection tool to generate atest image from the actual test reticle. More specifically, the modelsimulates how an e-beam is generated and impinged onto the simulatedreticle and simulates how secondary electrons are then detected by theinspection tool's optics and sensors and simulates a reference imagebased on such detected secondary electrons.

A first set of tunable model parameters for simulating a reference imagebased on the design data may first be selected in operation 904. Thismodel is also applied to the design data to generate a simulatedreference reticle image in operation 904. Since defects typicallyrepresent a small percentage of the pixels in a reticle image, amajority of the modeled reference reticle image's pixels, except fordefects, will match the test image when the tunable model parametershave been optimized. That is, when the model most closely simulates theprocess used to make the actual test reticle based on the design data(without defects) and the optics used to obtain a test image from suchsimulated reticle by the chosen inspection tool, the simulated referenceimage will also tend to closely match the test image. Thus, once theparticular reticle process that was used to make the test reticle andthe inspection tool that was used to generate the test image areunderstood and correctly modeled, an accurate reference image that mostclosely matches the test image (and how it was formed) can be simulated.

The tunable parameters of the model may take any suitable form forgenerating a corresponding reticle image. The tunable parameters maypertain to reticle writing characteristics, such as corner roundingamount, reticle material properties (e.g., composition and dimensions),pattern density dependent bias, etc., for constructing a referencereticle from the design data and inspection tool characteristics, suchas incident and detection aperture settings, focus, aberrationcharacteristics, voltage settings, pixel size, incident angle, etc., formodeling the same inspection tool that is being used to generate thetest image from the test reticle. The inspection tool model is appliedto the modeled reference reticle pattern to construct a reference imagebased on the design data. The modeled reference image corresponds to howa reticle that is constructed with the design data without any defectsis imaged onto the inspection tool's sensor.

After the model is applied to the design data using each set of selectedtunable parameters, it may then be determined whether an optimum matchbetween the generated reference image and the corresponding test imagehas been reached in operation 906. For instance, each particular testpatch image is compared to its corresponding reference patch image thatwas generated from the design database portion. Each test image andcorresponding reference image may comprise a plurality of pixels havingvarying intensity values. Alternatively, the test and reference reticleportions may be represented by a plurality of intensity values for theplurality of xy positions in the reticle portion.

The tunable parameters will result in an optimum match after aparticular number of iterations are performed through selectingdifferent combinations of tuning parameter values. For instance, anoptimum match may correspond to a set of parameters that result in aminimum difference between the test image and modeled reference image.An optimum match may be defined as the condition when a norm ofdifference of two images cannot be substantially reduced by changingadjustable parameters of the match. A suitable norm is the square rootof the sum of squares of pixel by pixel differences of the two images orsum of squares of the differences.

In the illustrated embodiment, if the optimum match between theparticular reference and test image has not been found, a next set oftunable parameters are selected for the model, which is applied to thedesign data to produce a new reference image in operation 904. A nextset of parameter values are repeatedly selected in operation 904 untilan optimum match between the reference and test image has been found.

Once an optimum match is found, the differences between the test imageand the reference image may also be flagged and stored as a patterndefect image in operation 908. These defects may also be analyzed todetermine whether such defects are within specifications as describedfurther herein. For example, the defects can be analyzed to determinewhether such defects represent real defects, fault defects, or noise.

A die-to-die or cell-to-cell inspection approach may also be utilizedfor the patterned EUV reticle.

Pattern orientation may also be factored into the process for detectingdefects so as to separately consider such pattern differences due toorientation. For example, a design template may be used to specifyparticular pitch and orientation values for particular reticle portions.Alternatively, the design data patterns may be analyzed to locateparticular patterns, such as one dimensional horizontal or verticallines or spaces. For example, the inspection process may be performedseparately for different reticle areas that have different pitch andorientations. In a specific implementation, vertical features areanalyzed separately from horizontal features since the orientation ofthe features with respect to an angled incident beam will affect theresulting intensity differently, referred to as the “shadow effect” onthe EUV scanner. As a result, even though certain patterns are intendedto be the same on the final wafer regardless of their orientations,those patterns on the EUV reticle may have different sizes depending ontheir orientation with respect to the EUV scanner. Therefore, theirsimulation results can be different enough that horizontal and verticalfeatures can be considered separately. That is, a reference image forthe horizontal features can be obtained separately from a referencedimage for the vertical features. These separate reference images canthen be separately subtracted from the respective test image features.The final, difference images can then be combined or kept separate forcorrection of the photolithography process.

Referring back to FIG. 3, it may then be determined whether the reticlepasses inspection in operation 306. If the reticle passes inspection,such reticle may be used for fabricating a wafer in operation 310. Ifthe reticle fails inspection/measurement, the reticle may be discardedor repaired if possible in operation 308. For instance, certain defectscan be cleaned or removed from the reticle. After repair, an inspectionmay be performed on the reticle at any time and the procedure 300repeated. One such repair tool is Zeiss's CDC tool.

The resulting inspection results may be utilized in any suitable mannerto determine whether the reticle should and can be repaired. Forinstance, an automated process may determine whether any patterndifference is above (or below) a predefined threshold. If a patterndifference is above (or below) the predefined threshold, thecorresponding reticle portion may then be more carefully reviewed todetermine whether the reticle is defective and can no longer be used(without reticle repair). For instance, a user may review the images ofthe defective areas, including the pattern defects and phase defectlocation images, to determine whether the corresponding reticle patternareas are actually out of specification. Other analysis techniques todetermine how the reticle defect would likely affect the wafer may beused.

FIG. 10 is a flow chart illustrating an inspection analysis procedure1000 in accordance with a specific embodiment of the present invention.Initially, the phase defect map, pattern defect map, and reticle patternmay be aligned in operation 1002. For instance, the image of the phasedefects and the image of the pattern defects are overlaid on the reticlepattern. FIG. 11 is a simplified example of a phase defect image and apattern defect image overlaid on a reticle pattern image in accordancewith one example. As shown, phase defects 804 a and 804 b and patterndefect 1104 are overlaid on the reticle image 800 with respect toreticle fiduciaries 802 a, 802 b, and 802 c. The reticle image 800includes reticle patterns 1102 a and 1102 b, which are also shown withrespect to the reticle fiduciaries. Reticle pattern defect 1104 is shownas a widening of pattern line 1102 b. For instance, the fiducials in thereticle pattern image, reticle defect image, and phase defect image maybe aligned. Alternatively, previously stored coordinates for each defectmay be used to map the defect images to a reticle pattern image. Thesestored coordinates all used the same reference, such as the reticlefiducials. Accordingly, the defect images can be accurately viewed inrelation to the reticle pattern.

A wafer exposure pattern that would result from the current reticlepattern, which includes pattern defects, and phase defects, may also besimulated in operation 1004. For instance, PROLITH™ available fromKLA-Tencor of Milpitas, Calif. may be used to simulate the exposurepattern of the wafer based on the current reticle pattern and phasedefect information, such as defect location and size. For instance, theimaging of the reticle pattern onto a modeled photoresist layer using aparticular photolithography tool is modeled so as to simulate an aerialimage of the exposure pattern in a photoresist layer.

It may then be determined whether each defect (phase or pattern defect)is a problem in operation 1006. For example, differences between asimulated exposed pattern image, which can be based on the reticle anddefect data, and a reference image may be determined. Differences thatare above a predetermined threshold may be determined to be a problemthat requires correcting or discarding the reticle.

Data in the design database representing a layout of the reticle may beused to generate a reference image. The reference image is a simulatedimage that would be formed on a specimen using a specific reticle and anexposure system having specific exposure conditions if the reticlepattern did not include any printable defects. In addition, thereference image substantially corresponds to an image of the reticlethat would be formed on a wafer by an exposure system under a particularset of exposure conditions.

A design database may also include designations as described above. Thedesignations may include, for example, flags or tags associated withdifferent types of regions, features, or portions of features. Thedesignations, however, may include any identification suitable todistinguish one type of region, feature, or portion of a feature fromanother type. Each region, feature, or portion of a feature on thereticle may be associated with a designation. Data in the designdatabase representing a layout of the reticle may be separate from datain the design database representing the designations. In addition,different types of designations may be separated in the design database.For example, the design database may include a first set of data thatincludes designations for critical regions, features, or portions offeatures on the reticle and a second set of data that includesdesignations for non-critical regions, features, or portions of featureson the reticle. Alternatively, different designations may be combinedinto a single set of data.

A designation may indicate to the inspection system an inspection methodto be performed on a portion of the reticle associated with thedesignation. Such designations may also be used by an inspection systemduring inspection of a specimen, such as an integrated circuitfabricated using the reticle. In addition, or alternatively, adesignation may indicate to a processor one or more functions such as adetection algorithm to be performed on data generated by an inspectionsystem in a portion of the reticle associated with the designation. Inthis manner, different procedures can be used by the processor to detectdefects on the reticle in different portions of the reticle. In acritical region, for example, a designation may indicate a morestringent threshold and/or a particular algorithm that may be used todetect defects. In some instances, the designations may be used toindicate only those regions of the reticle to be inspected or only thoseregions of the reticle not to be inspected. In addition, multipledesignations may be associated with a portion of the reticle, and eachdesignation may indicate a different parameter of the detectionprocedure. For example, a first and a second designation may be used toindicate a threshold and an algorithm, respectively, that are to be usedfor detecting defects in a single portion of a reticle. In addition,such designations may also be used by a process tool such as a patterngenerator or a reticle writer to indicate to the process tool parametersof a process to be used to fabricate a reticle or an integrated circuitusing the reticle.

Referring back to FIG. 10, a reticle repair may then be simulated andsuch reticle repair's effectiveness may be determined for each problemdefect in operation 1008. If valid reticle repairs are found for allproblem reticle defects, such reticle repairs may then be implemented inoperation 1010. Otherwise, the reticle is discarded.

Combining optical inspection of the reticle blank with an e-beaminspection of the patterned reticle gives a complete picture of EUVreticle quality. The combined inspection results from the optical ande-beam inspection tools can also be used to simulate the effects of thedetected phase defects and of the pattern defects on thelithographically printed integrated circuit and to determine whether thedefect needs to be repaired or compensated.

Inspection System Examples

Techniques of the present invention may be implemented in any suitablecombination of hardware and/or software system. FIG. 12 is adiagrammatic representation of an example inspection and lithographysystem 1200 in which techniques of the present invention may beimplemented. As shown, the system 1200 includes an optical inspectiontool 1204 for inspecting a blank reticle (or other specimens) fordefects, an e-beam inspection tool 1202 for detecting pattern defects ona patterned EUV reticle and obtaining high-resolution images of defects,one or more lithography systems 1210 for fabricating and using an EUVreticle, a network (e.g., switched network 1206) for allowingcommunication between the inspection lithographic system components, andan optional mass storage device 1208. Any of the inspection orlithography systems may also include one or more inspection/lithographycontrol and/or review stations for setting up the inspection andlithography systems and reviewing the defect data, images, and maps.Each device of the inspection and lithography system typically mayinclude one or more microprocessor integrated circuits and may alsocontain interface and/or memory integrated circuits and may additionallybe coupled to one or more shared and/or global memory devices forstoring the setup recipes and inspection results.

The various components and tools may be implemented as separate devicesor implemented in an integrated cluster system. The system 1200 may alsoinclude a data distribution system for distributing image or detectiondata via network 1206, as part of or separate from each inspectionsystem. The data distribution system may be associated with one or morememory devices, such as RAM buffers, for holding at least a portion ofthe received data. Preferably, the total memory is large enough to holdan entire swath of data. For example, one gigabyte of memory works wellfor a swath that is 1 million by 1000 pixels or points.

Each component of the system 1200 may comprise a specially configuredcomputer system that includes program instructions/computer code forperforming various operations described herein that can be stored on acomputer readable media. Examples of machine-readable media include, butare not limited to, magnetic media such as hard disks, floppy disks, andmagnetic tape; optical media such as CD-ROM disks; magneto-optical mediasuch as optical disks; and hardware devices that are speciallyconfigured to store and perform program instructions, such as read-onlymemory devices (ROM) and random access memory (RAM). Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter.

The optical inspection apparatus 1204 may be suitable for inspectingsemiconductor devices or wafers and optical reticles, as well as EUVreticles or masks. One suitable inspection tool is the Teron™ reticleinspection tool available from KLA-Tencor of Milpitas, Calif. Othertypes of samples which may be inspected or imaged using the inspectionapparatus of the present invention include any surface, such as a flatpanel display.

An optical inspection tool may include at least one light source forgenerating an incident light beam, illumination optics for directing theincident beam onto a sample, collection optics for directing an outputbeam that is emitted from the sample in response to the incident beam, asensor for detecting the output beam and generating an image or signalfor the output beam, and a controller for controlling the components ofthe inspection tool and facilitating the inspection techniques asdescribed further herein.

In the following exemplary inspection systems, the incident beam may bein any suitable form of light. Additionally, any suitable lensarrangement may be used to direct the incident beam towards the sampleand direct the output beam emanating from the sample towards a detector.The output beam may be reflected or scattered from the sample ortransmitted through the sample, depending upon the particular inspectionor metrology application. For EUV reticle inspection, the output beam isreflected from the sample. Likewise, any suitable detector type ornumber of detection elements may be used to receive the output beam andprovide an image or a signal based on the characteristics (e.g.,intensity) of the received output beam.

The inspection tool may be generally operable to convert such detectedlight into detected signals corresponding to intensity values. Thedetected signals may take the form of an electromagnetic waveform havingamplitude values that correspond to different intensity values atdifferent locations of the reticle. The detected signals may also takethe form of a simple list of intensity values and associated reticlepoint coordinates. The detected signals may also take the form of animage having different intensity values corresponding to differentpositions or scan points on the reticle. An intensity image may begenerated after all the positions of the reticle are scanned andconverted into detected signals, or potions of an intensity image may begenerated as each reticle portion is scanned with the final intensityimage being complete after the entire reticle is scanned.

In certain inspection applications, the incident light or detected lightmay be passed through any suitable spatial aperture to produce anyincident or detected light profile at any suitable incident angles. Byway of examples, programmable illumination or detection apertures may beutilized to produce a particular beam profile, such as dipole,quadrapole, quasar, annulus, etc. In a specific example, pixelatedillumination techniques may be implemented. Programmable illuminationsand special apertures can serve the purpose of enhancing featurecontrast for certain patterns on the reticle.

FIG. 13 is a diagrammatic representation of some elements of an opticalinspection tool 1300 in which techniques of the present invention may beimplemented. The optical inspection tool 1300 includes a light source1302 that is suitable for inspection of an EUV reticle. One example of alight source is a quasi-continuous wave laser. In certain embodiments, alight source may generally provide high pulse repetition rate,low-noise, high power, stability, reliability, and extendibility. It isnoted that while an EUV scanner operates at 13.5 nm wavelength, aninspection tool for an EUV reticle does not have to operate at the samewavelength. A Teron™ system from KLA-Tencor operating at 193 nm has beenproven to be able to inspect EUV reticles.

A light source may include a beam steering device for precise beampositioning and a beam conditioning device, which can be used to providelight level control, speckle noise reduction, and high beam uniformity.Beam steering and/or beam conditioning devices may be separate physicaldevices from, for example, a laser.

An inspection system includes a collection of optical elements forfocusing an illuminating light beam onto the inspected surface 1312. Forbrevity, FIG. 13 illustrates only a condenser lens 1304, an imaging lens1308, a detector lens 1313, and a beam splitter 1306. However, oneskilled in the art would understand that an inspection system caninclude other optical elements needed to achieve specific inspectionfunctions. The imaging lens can be adjusted to different sizes ofpixels, e.g., less than about 100 nm for each pixel or, moreparticularly, less than about 75 nm or even less than 60 nm.

The sample 1310 may also be placed on a stage (not labeled) of theinspection system 1300, and the inspection system 1300 may also includea positioning mechanism for moving the stage (and sample) relative tothe incident beam. By way of examples, one or more motor mechanisms mayeach be formed from a screw drive and stepper motor, linear drive withfeedback position, or band actuator and stepper motor.

After the incident beam(s) impinge on the sample 1310, the light maythen be reflected and scattered from the sample 1310 in the form of“output light” or an “output beam” (or multiple output beams). Theinspection system also includes any suitable lens arrangements fordirecting the output light towards one or more detectors. As shown, areflected beam can be received by a detector 1314 via lens 1308,splitter 1306, and lens 1313. In certain embodiments, the detector 1314is a time delay integration (TDI) detector. A typical TDI detectoraccumulates multiple exposures of the same area of the inspectedsurface, effectively increasing the integration time available tocollect incident light. The object motion is synchronized with theexposures to ensure a crisp image. In general, a detector may includetransducers, collectors, charge-coupled devices (CCDs) or other types ofradiation sensors.

FIG. 13 shows an example where an illuminating light beam is directedtowards the sample surface 1312 at a substantially normal angle withrespect to the inspected surface. In other embodiments, an illuminatinglight beam can be directed at an oblique angle, which allows separationof the illuminating and reflected beams. In these embodiments, anattenuator may be positioned on the reflected beam path in order toattenuate a zero order component of the reflected light beam prior toreaching a detector. Furthermore, an imaging aperture may be positionedon the reflected beam path to shift the phase of the zero ordercomponent of the reflected light beam. An illumination aperture may alsobe positioned on the illumination path to achieve various illuminationprofiles.

A detector is typically coupled with a processor system 1316 or, moregenerally, to a signal processing device, which may include ananalog-to-digital converter configured to convert analog signals fromthe detector 1314 to digital signals for processing. The processorsystem 1316 may be configured to analyze intensity, phase, and/or othercharacteristics of one or more reflected beams. The processor system1316 may be configured (e.g., with programming instructions) to providea user interface (e.g., a computer screen) for displaying a resultanttest image and other inspection characteristics. The processor system1316 may also include one or more input devices (e.g., a keyboard,mouse, joystick) for providing input. The processor system 1316 may alsobe coupled with the stage for controlling, for example, a sampleposition (e.g., focusing and scanning) and other inspection parametersand configurations of the inspection system elements. In certainembodiments, the processor system 1316 is configured to carry outinspection techniques detailed above.

Any suitable e-beam tool may be used to efficiently detect patterndefects and obtain high-resolution images at locations of the phasedefect detected by an optical tool. In one embodiment, a chargedparticle tool, such an electron beam tool, having multiple beam columnsis utilized. In one example, the e-beam tool has more than 25 beamcolumns for scanning simultaneously across the reticle. Several suitablemultiple column e-beam systems are described further in InternationalPCT application, having Publication No. 2013/003371, filed 26 Jun. 2012,and U.S. Patent Application, having Publication No. 2013/0001418, filed25 Jun. 2012. These applications are incorporated herein by reference intheir entirety. These multiple columns can be simultaneously scannedacross the entire reticle in 4-5 hours, as compared to currentsingle-beam systems that require 100 hours or more. However, singlecolumn e-beam systems can also be used.

In specific implementations, an e-beam inspection tool may generallyinclude a multiple column head having a 10×10 array of columns (100) ora 14×14 array of columns (196). Thus, an inspection of a 100×100 mm2reticle area can be 4 hours or less using such high number of columns.The e-beam tool may also include a plurality of such multiple columnheads to achieve even faster inspection times.

In a specific multiple-column e-beam inspection system, multiple lensingfields may be produced by immersing a magnetic block of material havingan array of bores into the large-scale magnetic field. The locations ofthe bores define the locations of the columns. The large-scale B-fielddecays as it enters the bores from either end, thereby producing twolenses—one at the end towards the source, and one at the end towards thetarget substrate. In addition, the B-field effectively contains thesecondary electrons emitted from the sample under examination, allowingthem to be swept back up each of the columns so as to be detected.Signal contamination due to electron spillage to adjacent columns isnegligible.

The electrostatic elements in each column provide the capability toraster the electron beam with varying landing energies and extractionfields for various inspection use cases. The scanning among the columnsmay be synchronous and may be performed along a single direction, normalto the stage travel direction, so as to cover the wafer area in swaths.

FIG. 14 is a cross-sectional diagram of a multiple-column electron beamapparatus 1400 in which certain techniques of the present invention maybe implemented. The apparatus 1400 includes an electromagnet for thelarge-scale (global) magnetic circuit. The electromagnet may include aconductive coil 1403 wound around a magnetic yoke 1402 and may beconfigured to produce a large-scale, magnetic field (B field) 1404 in aregion between an upper magnetic pole piece (pole) 1406 and a lowermagnetic pole piece (pole) 1408. Note that one position of theconductive coil 1403 about the yoke 1402 is depicted in the embodimentshown in FIG. 14. The conductive coil 1403 may be arranged at otherpositions in alternate embodiments.

The large-scale B field 1404 may be configured to be homogeneous(uniform) in the region between the upper and lower poles (1406 and1408) without the presence of the multiple-column array 1410. Themultiple-column array 1410 may be arranged within the region of thelarge-scale B field 1404.

The multiple-column array 1410 may be formed using a magnetic fluxby-pass plate 1412 with multiple bores 1413 that perturb the large-scaleB field 1404 so as to produce lensing fields for each of the columns inthe array 1410. The lensing fields are formed at both of the ends ofeach bore 1413 due to the decay of the large-scale B field 1404 as itenters each end of each bore 1413. The flux by-pass plate 1412 may bemade of magnetic steel, for example.

The flux by-pass plate 1412 may be a single monolithic plate.Alternatively, the flux by-pass plate 1412 may be formed using twoplates (upper and lower) to allow applying different voltages to theupper and lower portions. As another alternative, the flux by-pass plate1412 may be divided in the x-y (horizontal) dimensions to allowadjusting the voltage on each individual bore 1413.

Further components may be included so as to use each bore 1413 as amicro-column for the generation and focusing of an individual electronbeam. These components generally include an electron source 1414 andmultiple column elements 1416 arranged to be adjacent to each bore 1413.An exemplary implementation of these components is described below inrelation to the embodiment of an individual micro-column depicted inFIG. 15.

The column array 1410 is configured to individually focus the multipleelectron beams onto the surface of a reticle 1418 (or wafer or othersubstrate) positioned below the bottom end of the bores 1413. The columnarray 1410 may include a two-dimensional array of electron beam columns,where each column may be formed by arranging appropriate components inand about a bore 1413.

The target reticle (or other manufactured substrate, such as a wafer)1418 may be held by a movable stage 1420. In FIG. 14, the stage 1420 maybe configured to move the reticle 1418 under the column array 1410 inthe direction perpendicular to the plane of the page. In an exemplaryimplementation, the stage 1420 may be configured to use cross-rollerbearings to be movably supported above the lower yoke 1408, and theheight of the stage 1420 above the lower yoke 1408 may be adjustable.

FIG. 15 is a cross-sectional diagram of a single micro-column formedwithin magnetic material 1530 in accordance with an embodiment of theinvention. The magnetic material 1530 may be that of a flux by-passplate 1412 per the embodiment of FIG. 14. The micro-column may beconfigured to generate an electron beam that travels down the bore 1413along the optical axis 1510 of the column. As shown, the components ofthe micro-column may include an emitter 1501, an extraction aperture1502, a resistive liner 1504, a gun lens electrode 1506, a groundedelectrode 1508, a column aperture 1512, one or more auxiliary electrodes1514, and an extractor electrode 1516.

In one embodiment, each bore 1413 formed through magnetic material maybe cylindrical and may be 9.5 mm in length and 0.5 mm in diameter. Otherbore dimensions may be implemented in other embodiments. Note that thebore 1413 need not be symmetric in that it may have different entranceand exit hole sizes.

The electron source 1414 may have an emitter 1501, to which is applied ahighly negative voltage Vemitter. The extraction aperture 1502 may beformed from an electrode with an opening therein. The electrode may havea voltage Vextractor applied thereto that is positive relative toVemitter so as to extract electrons from the emitter 1501. The extractorvoltage may be set to provide the desired current and angular intensityof extracted electrons.

The resistive liner 1504 may be arranged around the bore 1413, and suchresistive liner may be used to shield the field of the electrodes of thebore from the potential on the magnetic material 1530 of the bore.

The voltage on the magnetic material 1530 of each bore may be set to apotential determined by the mode of operation. In one implementation,the voltage on the magnetic material 1530 of each bore may be set so asto act as a suppressor for charge control at the target reticle (orother manufactured substrate) 1418.

The gun lens electrode 1506 may be comprised of one or multipleelectrodes arranged around a portion of the bore 1413 in the uppercolumn. The gun lens electrode 1506 of each bore may have a voltage Vgunapplied to it so as to condense the electrons into an electron beam.

The grounded electrode 1508 may be arranged around a portion of the bore1413 beneath the gun lens electrode 1506, and such grounded electrode isconductively connected to an electrical ground of the apparatus. Assuch, the grounded electrode of each bore is at a potential that is|Vemitter| higher (more positive) than the emitter 1501 of the bore.Hence, the electrons of the electron beam traveling down the opticalaxis 1510 of the micro-column will have an energy of approximatelye|Vemitter| as it passes by the grounded electrode 1508. The groundedelectrode 1508 may also function as a centering deflector which acts tocenter the electron beam through the column aperture 1512.

For example, Vemitter may be negative 3 kilovolts (3 kV) such that thebeam energy e|Vemitter| would be three kilo electron volts (3 keV).Other beam energies may be generated by applying different voltages tothe emitter. The gun lens electrode 1506 and the grounded electrode 1508may be spaced apart in order to maintain inter-electrode fields betweenthe electrodes (1506 and 1508) below a threshold field strength. In oneembodiment, for example, if the potential difference between theelectrodes (1506 and 1508) is approximately 3 kV, then in order tomaintain the inter-electrode fields below a threshold field strength of4 kV/mm, the electrodes (1506 and 1508) would be spaced apart by atleast 0.75 mm since 3 kV/0.75 mm=4 kV/mm. In other embodiments, theinter-electrode fields may be maintained below other threshold fieldstrengths by appropriate electrode spacing.

The column aperture 1512 may be arranged around the optical axis 1510below the grounded electrode 1508. The column aperture 1512 separatesthe upper column which includes components relating to the electron gunfrom the lower column which includes components relating to beamdeflection and the magnetic objective lens.

The auxiliary electrode(s) 1514 may comprise one or multiple electrodesarranged around a portion of the bore 1413 beneath the column aperture1512. In one implementation, two auxiliary electrodes 1514 may be usedin each bore 1413. The resistive liner 1504 may be used to shield thefield of the auxiliary electrode(s) 1514 from the potential on the fluxby-pass plate 1412. The auxiliary electrode(s) 1514 may function as afirst electrostatic component to which an appropriate voltage may beapplied to reduce aberrations in the electron beam.

The extractor electrode 1516 may comprise one or multiple electrodesarranged around a portion of the bore 1413 beneath the auxiliaryelectrode(s) 1514. The resistive liner 1504 may be used to shield thefield of the extractor electrode 1516 from the potential on the polepiece of the central yoke 1412. The extractor electrode 1516 mayfunction as a second electrostatic component to which an appropriatevoltage may be applied to reduce aberrations in the electron beam. Inone embodiment, the auxiliary electrode(s) 1514 and the extractorelectrode 1516 may be spaced apart so as to maintain an inter-electrodefield strength below the threshold field strength described above.

The manufactured substrate 1418 may be arranged to be a distance RDbelow the magnetic material 1530 which surrounds the bottom end of thebore 1413 that defines the micro-column. In one embodiment, RD issufficiently long so as maintain the field strength between the magneticmaterial 1530 and the manufactured substrate 1418 below the thresholdfield strength described above.

As described above in relation to FIG. 14, the magnetic material 1530and the manufactured substrate 1418 are immersed in the large-scale Bfield 1404. The presence of the magnetic material 1530 which surroundsthe bottom end of the bore 1413 within the large-scale B field 1404causes the large-scale B field 1414 to effectively decay as itapproaches the bottom end of the bore 1413. The resultant fieldeffectively forms an objective magnetic lens which focuses the electronbeam onto the surface of the reticle 1418.

In one embodiment, the micro-column may be configured for electron beamimaging. In this case, a detector 1518 may be provided in themicrocolumn. The detector 1518 may be implemented as a PIN diodedetector and may be positioned beneath the column aperture 1512. In thisembodiment, the resultant B field, which forms the objective magneticlens, also acts to contain secondary electrons emitted from the reticle1418. This arrangement allows the secondary electrons to pass back upthrough the bore 1413 of the micro-column towards the detector 1518.

It should be noted that the above description and drawings are not to beconstrued as a limitation on the specific components of the system andthat the system may be embodied in many other forms. For example, it iscontemplated that the inspection or measurement tool may have anysuitable features from any number of known imaging or metrology toolsarranged for detecting defects and/or resolving the critical aspects offeatures of a reticle or wafer. By way of example, an inspection ormeasurement tool may be adapted for bright field imaging microscopy,dark field imaging microscopy, full sky imaging microscopy, phasecontrast microscopy, polarization contrast microscopy, and coherenceprobe microscopy. It is also contemplated that single and multiple imagemethods may be used in order to capture images of the target. Thesemethods include, for example, single grab, double grab, single grabcoherence probe microscopy (CPM) and double grab CPM methods.Non-imaging optical methods, such as scatterometry, may also becontemplated as forming part of the inspection or metrology apparatus.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. It should be noted that there are many alternative waysof implementing the processes, systems, and apparatus of the presentinvention. Accordingly, the present embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein.

What is claimed is:
 1. A method of inspecting an extreme ultraviolet(EUV) reticle, the method comprising: using an optical inspection toolto obtain a phase defect map for the EUV reticle before a pattern isformed on the EUV reticle, wherein the phase defect map identifies aposition of each phase defect on the EUV reticle; after the pattern isformed on the EUV reticle, using a charged particle tool to obtain animage of each reticle portion that is proximate to each position of eachphase defect as identified in the phase defect map; displaying orstoring the phase defect map and one or images of each reticle portionthat is proximate to each position of each phase defect so as tofacilitate analysis of whether to repair or discard the EUV reticle;after the pattern is formed on the EUV reticle, using a charged particletool to obtain a pattern defect map for the EUV reticle, wherein thepattern defect map identifies a position of each pattern defect on theEUV reticle; and displaying and/or storing the pattern defect map inassociation with the phase defect map and one or images of each reticleportion that is proximate to each position of each phase defect so as tofurther facilitate analysis of whether to repair or discard the EUVreticle.
 2. The method as recited in claim 1, further comprising: priorto using the EUV reticle in a photolithography process, simulating anexposure pattern that would result from each pattern defect and phasedefect on the EUV reticle based on the phase defect map and the patterndefect map; prior to using the EUV reticle in a photolithographyprocess, analyzing the simulated exposure pattern to determine whetherone or more pattern or phase defects are predicted to cause a problem ina device that is fabricated with the EUV reticle and whether suchproblem can be mitigated by altering the pattern of the EUV reticle,wherein simulating and analyzing the simulated exposure pattern areperformed without use of a design database that was utilized tofabricate the EUV reticle; and if one or more pattern or phase defectsare predicted to cause a problem that can be mitigated, altering thepattern of the EUV reticle so as to mitigate the problem.
 3. The methodas recited in claim 1, wherein the position of each phase defect isreferenced with respect to a first stage coordinate system of theoptical inspection tool and the position of each pattern defect isreferenced with respect to a second stage coordinate system of thecharged particle inspection tool.
 4. The method as recited in claim 3,wherein both the first and second stage coordinate systems are based ona plurality of fiducial marks of the EUV reticle.
 5. The method asrecited in claim 1, wherein the pattern defect map is obtained bycompensating for design differences between reticle portions that aredesigned to result in identical exposed patterns when using the EUVreticle in a photolithography process and are designed to compensate forat least a flare effect of the photolithography process.
 6. The methodas recited in claim 1, wherein the pattern defect map is obtained viamultiple beams of the charged particle tool scanning simultaneouslyacross the EUV reticle.
 7. The method as recited in claim 6, wherein themultiple beams have a number greater than
 25. 8. The method as recitedin claim 1, further comprising: prior to forming the pattern on the EUVreticle, analyzing a position of each of a plurality of phase defects asidentified by the phase defect map relative to a design pattern, whichcan be used to form the pattern on the EUV reticle, to determine whethersuch phase defect is predicted to cause a problem in a device that isfabricated with the EUV reticle after it is patterned with the designpattern and whether such problem can be mitigated by altering the designpattern of the EUV reticle; and if one or more phase defects arepredicted to cause a problem that can be mitigated, altering the designpattern and using the altered design pattern to form the pattern on theEUV reticle so as to mitigate the problem.
 9. A system for inspecting areticle, comprising: an optical inspection tool configured to inspect aEUV reticle, which is unpatterned, and generate a phase defect map thatspecifies a plurality of phase defects and their associated positions onthe EUV reticle; a charged particle inspection tool configured toinspect the EUV reticle after a reticle pattern is formed on such EUVreticle and obtain a pattern defect map that specifies a plurality ofpattern defects and their associated positions on the EUV reticle,wherein the charged particle inspection tool is further configured toobtain an image at each phase defect's associated position on the EUVreticle; and an analyzer configured for determining whether one or morepattern or phase defects are predicted to cause a problem in a devicethat is fabricated with the EUV reticle and whether such problem can bemitigated by altering the pattern of the EUV reticle.
 10. The system asrecited in claim 9, wherein the analyzer forms part of the chargedparticle inspection tool.
 11. The system as recited in claim 9, whereinthe charged particle inspection tool and the optical inspection tool arein the form of an integrated cluster system.
 12. The system as recitedin claim 9, wherein the charged particle inspection tool is configuredto form a plurality of beam columns, the system further comprising areticle repair tool for repairing the EUV reticle if one or more patternor phase defects are predicted to cause a problem that can be mitigated.13. The system as recited in claim 12, wherein the beam columns areformed by using a magnetic flux by-pass plate with multiple bores thatperturb a large-scale B field so as to produce lensing fields for eachof the beam columns, wherein the charged particle tool includes themagnetic flux by-pass plate with multiple bores.
 14. The system asrecited in claim 12, wherein the charged particle inspection tool isconfigured to form more than 25 beam columns.
 15. The system as recitedin claim 9, wherein the position of each phase defect is referenced withrespect to a first stage coordinate system of the optical inspectiontool and the position of each pattern defect is referenced with respectto a second stage coordinate system of the charged particle inspectiontool and wherein both the first and second stage coordinate systems arebased on a plurality of fiducial marks of the EUV reticle.
 16. Anapparatus for reviewing inspection results for a EUV reticle,comprising: a display for displaying images; and a controller that isconfigured to perform the following operations: receiving a phase defectmap for a EUV reticle that was obtained before a pattern is formed onthe EUV reticle, wherein the phase defect map identifies a position ofeach phase defect on the EUV reticle; on the display, displaying animage of each reticle portion that is proximate to each position of eachphase defect as identified in the phase defect map; obtaining a patterndefect map for the EUV reticle after the pattern is formed on the EUVreticle, wherein the pattern defect map identifies a position of eachpattern defect on the EUV reticle; and analyzing the pattern defect mapin association with the phase defect map and one or images of eachreticle portion that is proximate to each position of each phase defectso as to determine whether to repair or discard the EUV reticle.
 17. Theapparatus as recited in claim 16, wherein the analyzing operationfurther comprises: prior to using the EUV reticle in a photolithographyprocess, simulating an exposure pattern that would result from eachpattern defect and phase defect on the EUV reticle based on the phasedefect map and the pattern defect map; and prior to using the EUVreticle in a photolithography process, analyzing the simulated exposurepattern to determine whether one or more pattern or phase defects arepredicted to cause a problem in a device that is fabricated with the EUVreticle and whether such problem can be mitigated by altering thepattern of the EUV reticle, wherein simulating and analyzing thesimulated exposure pattern are performed without use of a designdatabase that was utilized to fabricate the EUV reticle.
 18. Theapparatus as recited in claim 16, wherein the position of each phasedefect is referenced with respect to a first stage coordinate system ofthe optical inspection tool and the position of each pattern defect isreferenced with respect to a second stage coordinate system of thecharged particle inspection tool, wherein both the first and secondstage coordinate systems are based on a plurality of fiducial marks ofthe EUV reticle.
 19. The apparatus as recited in claim 16, wherein thepattern defect map is obtained by compensating for design differencesbetween reticle portions that are designed to result in identicalexposed patterns when using the EUV reticle in a photolithographyprocess and are designed to compensate for at least a flare effect ofthe photolithography process.
 20. The apparatus as recited in claim 16,wherein the apparatus in the form of a charged particle inspection toolconfigured to form multiple columns for scanning simultaneously acrossthe EUV reticle.
 21. The apparatus of claim 20, wherein the multiplecolumns have a number greater than
 25. 22. The apparatus as recited inclaim 21, wherein the multiple columns are formed by using a magneticflux by-pass plate with multiple bores that perturb a large-scale Bfield so as to produce lensing fields for each of the beam columns,wherein the charged particle tool includes the magnetic flux by-passplate with multiple bores.